[Clayart] glaze pops

[ronroy at ca.inter.net]

Hi Dan,

Your revision has a lower calculated expansion than the origional.

Why not try a completely different version using other materials. Lets  
say Neph Sy instead of custer and grollege or a ball clay istead of  
EPK. I don’t know how much patalite you have - wou;d you like to try  
some spodumene?

Let me know what other clays you have.

Perhaps keep the wollastonite unless you have reason to suspect it?

I am guessing but I think you are firing to cone 10?

RR

Quoting Pfeiffer Fire Arts <firearts at ardmore.net>:

> All,
>
>
> After a number of years of not having a lot of problems with pop's  
> in the glaze it has got so bad as to put us out of business. I have  
> been making small changes in our glaze to reduce the surface tension  
> hoping this would help. It has not and the last firing was the worst  
> of the lot. I am not sure there are 5 pieces that we can sell.
> This firing had a slow rise from 1700 to 1900 and then a hour dwell  
> at the top to cone 10 - 11. When slow about 2000 to give things time  
> to heel. If anything the pops are bigger with our new glaze then the  
> old one.
>
> Our first glaze base glaze is:
>
> Epk 			12
> Petalite 		14
> Wollastonite  	20
> Silca             20
> Custer         	33
> Bentonite 		1
>
> Our most recent attempt is to add a frit:
>
> Epk 			6
> Cal Epk		6
> Petalite 		15
> Wollastonite  	17
> Silca             20
> Custer         	29
> Bentonite 		.5
> Ferro 3134		6
> Veegum		.5
>
> While the calculated CEO is very close (8.60 and 8.61) to the same  
> for both versions we had some shivering when it was thick on one  
> piece.
> Anyone want to guess what to do next.
>
> Dan
> PfeifferFirearts.com
>
>



Ron Roy
ronroy at ca.inter.net
Web page ronroy.net